The Baby Brown uses an off cenered pivot to  gain a signal boosting mechanical  advantage. It achieves this  by placing the signal coil, in this case  a 1000 ohm headphone winding operating, as an electromagnet to gain eficiency  by focusing it's magnetic field on the shorter end of  the off centered pivoted armature  allowing the coil to leaverage  the  signal from a crystal set to drive the longer end of the pivot. P1 provided mechanical amplification at point P2  the lever driven speaker diaphram. It was placed at the base of the expanding trumpet to make a speach volume  level totally un reachable without some form of electrical amplification.  (eg  A step up transformer  thaking external power through a headphone driving a carbon microphone )

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